Aqueous dispersions of a thermoplastic resin of various types are known in the art. Aqueous dispersions have been used in a variety of fields since an aqueous dispersion prepared by using water as its dispersion medium can be more advantageous than the dispersions prepared by using an organic solvent for the dispersion medium in view of flammability, working environment, and/or handling convenience. For example, when an aqueous dispersion is applied and dried on a surface of a substrate such as paper, fiber, wood, metal, or plastic molded article, the coating formed can provide the substrate with water resistance, oil resistance, chemical resistance, corrosion resistance and/or heat sealability.
Aqueous dispersions of a thermoplastic resin have been produced by a process wherein a polymerizable monomer which is the resin raw material is polymerized by emulsion polymerization in an aqueous medium in the presence of a dispersing agent. This process is associated with the disadvantage of the limited number of the polymerizable monomers that can be used, and hence, the variety of the aqueous dispersions of the thermoplastic resin that can be produced, is limited. This process also suffers from complicated control of the polymerization reaction as well as intricate equipment.